STEALTH STUNNER
This beautiful 1970 280SL restomod is full of surprises
Article and photographs by Gary Anderson
Dick Osgood enjoys solving mechanical problems. An engineer by day at a Silicon Valley computer company until his retirement, with a thriving clock repair business on the side, Osgood also enjoyed restoring, maintaining and driving classic cars. But after a succession of Ford products – an AC Cobra, a Model A, and a Thunderbird – his wife was smitten by a W113 SL they saw at a classic dealer in San Jose, so they decided to look for a needy but restorable Pagoda. Knowledgeable mechanics in the area convinced them that they should look for a 280SL rather than the 230 or 250, and in late 2003 they found a good candidate near their home on eBay Motors, a 1970 280SL.
Acquired by the current owner in the early 1990s, the car was part of a collection of 10 classic cars. The previous history was murky, but the original sales slip indicated the first owner was a leasing company in Southern California. The recent repair receipts indicated that the car had suffered from long years of neglect between short intervals of repair and use by the collector. However, the price was attractive, leaving room for a reasonable amount of investment without exceeding the market value of average 280SLs.
Fixing the basic necessities, Osgood and his wife drove the car for about a year while deciding on a restoration strategy. During that year, Osgood worked on issues such as gauges and electrical accessories that didn’t work but were nearly inaccessible, an exhaust system that needed repairing but had been welded to the original downpipes to avoid pulling the engine, and smoky performance that pointed to inadequate oil changes during the last decade.
The biggest problem was that his wife refused to go out on the highway in the car because at 4,000 rpm in top gear at 70 mph, the noise was unbearable. And though he and his wife liked the color combination of the car, the exterior paint was faded and checkered, so a bare metal repaint would be required. After disassembling the car, Osgood sent it off to a friend’s shop to be repainted in the original chocolate brown paint formula so that unexposed areas would not need to be repainted. The only question his friend asked was whether Osgood wanted the finish to be show quality as opposed to factory quality. That would mean several more months in the shop to allow complete curing of the paint and extra wet and block sanding. Osgood readily agreed.
While the car was being painted, he considered the options. Osgood was absolutely committed to preserving the essence of the car – the styling and design that had attracted him and his wife to the model in the first place. Within that constraint, and because he was essentially rebuilding a car from the ground up, he decided to see if he could solve some of those problems he had encountered.
An engine rebuild could cost more than $10,000 and one of the rare optional “economy rear ends” that would reduce engine rpm at speed to a tolerable level might cost several thousand dollars more. However, living in northern California, a mecca for hot rods and custom cars, there was another option. Hot-rodder friends suggested he consider an engine swap.
After extensive research, Osgood decided that an engine swap would be the way to go. After considering a range of available crate engines, he found that a 1996 Ford Mustang 302 V-8 engine would fit neatly into the engine compartment without modifying the frame members or body panels, although extensions on the engine block would need to be fabricated. A Tremec 4-speed transmission with overdrive fifth gear and heavy-duty motorsport synchros would fit easily under the transmission tunnel on the original mounts and reduce engine rpm at highway speeds to a comfortable level. The total cost would be less than $4,000.
The exterior and interior of the car would be kept totally stock and original, with only the interior of the engine compartment giving away the car’s secret. The car could always be returned to original specifications, so the intrinsic value wouldn’t be affected, though Osgood had no intention of reselling it. The original engine and transmission went into another 280SL that had blown its engine, so that wouldn’t be wasted either.
Osgood knew very well that there’s no such thing as a “bolt-in” engine substitution, but he had confidence that among the various shops in the area, solutions could be found to the problems as they arose. An Edelbrock intake manifold and carburetor were an easy first choice and wouldn’t foul the hood panel. The Mallory Distributors specialist recommended a flat-cap distributor design that would provide the necessary clearance at the front of the engine. Palo Alto Speedos provided the proper drive for the VDO tachometer.
The sump pan had to be shortened to clear the existing chassis cross member, and buttresses were fabricated to strengthen the engine mounts. A local shop devised a new drive shaft that mated with the Ford universal joint in the front and the Mercedes universal joint at the rear. McCloud Clutch Company created a two-material pressure plate that provides smooth engagement of the V-8 engine and the transmission. A muffler specialist who enjoys a challenge fabricated a gorgeous set of headers, then mated them to a pair of exhaust pipes that fit under the SL body’s half-tunnel and produce a pleasing but powerful sound. By the time the work was completed, the engine had been in and out six times, but the entire team is very proud of the results. And the chassis has not been altered.
The bottom line from the power train changes is that at highway speeds, the engine is loafing at less than 2,400 rpm. With a drivetrain that weighs 200 pounds less than the original, handling is improved and Osgood gets an easy 18 miles per gallon around town. Although the engine produces 220 horsepower and 290 pound-feet at the flywheel, Osgood has no intention of finding out what it might do in the quarter-mile due to the use of the stock differential. His total investment, including the original purchase price – but exclusive of his own time, which he dismisses as being hobby time anyhow – is less than $45,000.
Has any sin been committed against the soul of the original car? We think not. By comparison with specialist companies in Germany that are tearing out entire drivetrains and reconfiguring body panels and chassis members to insert modern running gear into these lovely W113 bodies, Osgood’s actions seem benign. He now has an SL that is as eye-catching inside and out as any concours-original version on the road. More to the point, with these modifications, he’s much more likely to be enjoying it out on the road than would ever have been the case if he had retained the original drive train.
1970 MERCEDES-BENZ W113 280SL
TYPE: Two-door two-seat roadster with soft top and removable hardtop
ENGINE: 1996 Ford Mustang 302 V-8
TRANSMISSION: Tremec 5-speed with .6 to 1 overdrive 5th gear
HORSEPOWER: 220 at 5,200 rpm
TORQUE: 290 lb-ft at 3,800 rpm (at flywheel)
LENGTH: 168.8 in
CURB WEIGHT: 2,705 lb (est), 200 lb lighter than original engine
FUEL ECONOMY: 18 mpg (est)
Dick Osgood on the way to a local car show, out on the road enjoying the 280SL as it was meant to be enjoyed.
The interior of the car is absolutely stock original, and pristine, with the exception of a slightly lengthened center console to fit the Tremec transmission gear shift.
Under the hood is a different story, with the equally pristine Ford 302 engine for a 1996 Mustang. The engraved valve covers and Mercedes star on the air intake are tongue-in-cheek touches.
Externally, the car displays all the lovely beauty of the W113 roadsters.
Another view of the lovely 280SL displaying its gorgeous show-quality paint. 
Nothing on the exterior gives away the car’s secret. 
DIck Osgood has all the original paperwork for the car, including the manual for the optional Frigiking air conditioning. 
The dashboard, a/c system, and Nardi wheel are all period correct, with only a tasteful console modification to accommodate the five-speed transmission.